Ball suspended dynamic counterweight



30 eliminating crankshaft accelerations i BanrxsUsrENnEn DYNAMIC coUN'rlia- WEIGHT vNew York invention comprisesI improvements in s dynamic counterweights for the elimination o f C torsional vibrations ofthe'general type disclosed in my co-pending application, Serial N0. 7,475,

, led February 21, 1935.A That application shows i a counterweight member pendulously mounted on bers indicate similar parts and in which;

la'crankshaft member byrollers'rollably engaging holes' in each member, the vradius of pendulum swing being defined bythe diierenc in diameter between the rollers and* the holes. This formV of twin-roller suspension ,endows the .counterweight mass `with the properties ofy a) simple pendulum sinceevery pointon the mass swings thru'the same radius ofarc. When such a pendulumis associated with ro tating shaft, the restoring force is 'furnished "by i centrifugal force wherefore the pendulum period increases with the speed of rotation so that the i pendulum makes the same number ofv swings per revolution regardless of the speed of 'revolu- ':tion. It is known'that whenthe pendulum fre-y lquency is made equal to`the frequency of the torque impulses toy which the shaft is subject, then the pendulum mass will automatically swing 25 180? out of phase Ywith. the `exciting impulses which are thus neutralized.l

' 'I'his type of dynamic counterweight has gone intoextensive and successful use in radial Vair-` craft `*engines and has;l beenfound effective in end vibraitions in the rotational sense. However, incertain cases, it" has been foundv that crankshafts may be subject to "tuning-fork" or fore` and aft vibrations of the counterweights,

1 35 due tothe' elasticity of the craiikamis and `manlii pins. Should .the natural frequency. oi' vibration of the counterweight Vmas'sin this 'axial sense be come synchronous with the bending4 deilections to which the shaft is subject inoperation, fatigue l 40 failure .of the counterweight attachments is apt to occur. In the case of roller type dynamh: dempers, the slight relative Vaxialxnovement -hee.` `tween the counterweight and the/crankshaft` member from some such vibration has,'.in certain 45 cases, produced scumng or wear of the cylin\ drical rollers which are subiect'to sliding against their races shouldrelatlve axial displace? yments occur. .v i I Accordingly. a prime object of the'present in- Application ,lai'iiiaryea 1937, sei-iai No. 121,915

- 41'1 claims. cl. 'M -604i -vention yis to provides. means whereby the dy- .I

axial Vvibration between thecrankshaft .and the counterwight by rolling as distinct from sliding action. j l Other bjects'will be obvious from,".or will beA pointed out, fin, the following description, with 5 reference ;to the drawing in which similar num- Fig. 1 is an end view in part section on the line I-I of Fig. 2, 4

` Fig. 2 is a fragmentary side view and in part, 10 n' a section on the 'line 2--2 of Fig. 1, and Fig. 3 is a fragmentary plan view and in part, aV section o ri-theline3-3 of Fig. 1. f f u In the drawing l0 designates one endv of Va conventional crankpin to which afcrankcheek' lo I2 is secured by a conventional clamp bolt i4, the cheek being provided with the usual journal i6. The cheekis provided with an extension arm I8 furnished withtwo .lateral extensions or bosses in to which are fitted spherical cups or 20 socketsll.

A counterweight comprising two similar halves Y l 24-26 secured together by bolts 28 -isV disposed loosely around the ,extension18,freedomfor circumferential movement of the counterweightbe- 25 ing .providediby clearancesindicated at --31 Fig. l and, clearance'ior slightaxial movement being provided asfindicated at 34 Figs, 2 and 3.

The counterweight halves N-ZB, though similar to each other, are each formed with one thick end 30 '25 and one thin end 21, the thick end 25 of each halfhaving a "socket within which is fitted a hardened cup 36 having. a spherically concave` is made greater thanthe radius R'of the balls 33, the diierence being that appropriate to theA 40 l desired pendulum. frequency.

. It should lnow be clear that the counterweight 24--23 is supported against. centrifugal-forces'by z' the balls 38 and sockets 2 2-36 wherebyy thev counterweight is vfree for, pendulum movement both in .the plane of Fig. 1 and in the'plane or Fig. 2, that is' to say. both rotationally' and axially with respect to cranlrshaitf The countenweight,'according1y, comprises ajdamper effective against both torsional and tui'ngftork or axial 50 I vibrations since the balls'o .refree'l to'roll in any direction on the sockets 22. At .the same time, and regardless of the type. offvibration encountered, the ball willhave a` rolling as distinct' 4' from a sliding co-action with thefsockets whereby for a third, mode ofv motion i. e., it may swing Y type damper will be eliminated. This universal mounting of the counterweight gives it freedom about the radial axis from the center of the weight to the crankshaft center corresponding to a twistingvibration of the extension arm I8 or of the crankcheek I2 as a Whole. There is some evidence that the occasional scufllng of the cylin` drical rollers heretofore used in this type of damper may be the result of this mode of vibration of the crankshaft, and accordingly, the provision of a counterweight which shall be also effective in this manner is one of the objects of this invention. The lballs 38-38, with the coacting sockets, are .symmetrically disposed on each side of the plane of symmetry of the crankshaft assembly. Accordingly, as the counterweight moves relative to the shaft, the two-point suspension of the counterweight gives rise to simple pendulum characteristics therein, whereby all points in the weight may movev in an identical arcuate path, without polar movement of the Weight relative to the shaft.. This linear type of movement obtains for axial and rotational vibrations, which are predominant,` but slight polar vibration may occur upon twisting deflections of the crank extension about a radius of the crank shaft or pin'.

While I have described my inventionA in detail in its present preferredv embodiment, it will-be obvious to those skilled in the art,.after understanding my invention, that various 'changes and vmodifications may be made therein Without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

WhatIclaim is: l 1. In combination, a crankshaft extension member, a counterweight member loosely embracing said crankshaft memben opposed spherical cups formed4 in the respective members, and

' `balls rollably movable upon said cups upon relative rotational and longitudinal vmovement between said members.

2. A crankshaft having an extension provided with spherical ball seats facing towards the center of rotation of said shaft, a counterweight having spherical seats opposed to said crankshaft seats, balls rollably engaged betweensaid seats for supporting said counterweight for pendulous action longitudinally and transversely of said shaft.

3. In combination, a crank shaft having an extension member and a'counterweight, one loosely embracing the other, and having respectively opposed spherically curved ball race surfaces, `balls rollably engaging said surfaces for universal pendulous` support of said counterweight.

4.,Means for suppressing torsional and axial vibrations of a crankshaft comprising a crankshaft extensionY member and a counterweight member, one loosely embracing the other, and

a pendulous support for said weight comprising radii of the seats.

2,121,950 l the chaiing found in certain cases with the roller balls vrollably engaging opposed spherically curved pockets formed in the respective members.

5. In combination, a shaftextension member having a concave sphericallyv curved seat facing inwardly toward the shaft center, a counterweight member having va concave spherically curved seat opposed to said first seat, facing outwardly but lying inward of said first seat, and y a ball between said seats and rollably engaged therewith.

6. In combination, a shaft eiitension member, a counterweight member, one embracing the other and having rotational and longitudinal clearance relative to each other, concave spherically curved seats on the respective members, the seat on the counterweight facing outwardly but lying inwardly of the seat on/the extension,` said seats being opposed, and a ball of lesserradius than either of said seats yrollably contacted with -both seats.

7. In combination, a shaft extension member having laterally spaced inwardly facing concave spherically curved seats, a counterweight having outwardly facing concave spherically curved seats opposed to said first seats, the centers of said counterweight seats and the center of gravity of the counterweight normally lying in a common plane normal to the shaft axis, and balls rollably contacting opposed extension and counterweightl seats.

8. In combination, a shaft extension member and a counterweight member opposite thereto, a plurality ofopposed concave spherically curved seats on the respectively opposite members, and balls rollably engaged between opposed seats. l

9. In' combination, a shaft extension member and a counterweight member opposite thereto, a

plurality of opposed concave spherically curvedV seats on the respectively opposite members, balls rollably engaged between opposed seats and said 11.l In combination with a shaft, an extension of the shaft having a concave spherically curved l seat facing substantially inwardlyy toward the center of rotation, a weight having a concave spherically curved .seatopposed to said first seat, and an element having spherically formed portions between andcontacting respective seats. 1 ROLAND CHILTON. 

